WO2007110147A1 - Method of welding a wear layer onto a parent material using a plurality of flux-cored wire electrodes, metal powder and welding powder - Google Patents

Abstract

The present invention relates to a method of welding a wear layer onto a parent material (8), wherein a welding current is applied in each case to a first wire electrode (5) and at least one second wire electrode (5a), which are continuously fed to the parent material (8) for producing a common weld pool, wherein metal powder (7) is fed to the weld pool, wherein welding powder (6) is fed to the weld pool, wherein the wire electrodes are flux-cored wire electrodes (5, 5a), having a core (10) and a covered electrode (11), wherein the flux-cored wire electrode (5, 5a) has a higher alloy than the weld deposit analysis of the wear layer (9) to be welded on, wherein the covered electrode (11) of the flux-cored wire electrode (5, 5a) consists of an alloy which has magnetization properties suitable for the adhesion of the metal powder (7).

Description

METHOD FOR REINFORCING A UTILIZING LAYER ON A BASE MATERIAL USING MULTIPLE FILLER ELECTRODES, METAL POWDERS AND WELDING POWDERS

The present invention relates to a method for welding a wear layer to a base material, in particular a sub-contracting welding method according to the preamble of

Claim 1.

Submerged arc welding is a well-known process technology that is used almost exclusively for fully mechanized welding operations. She has the priority application at

Joint welds, because this is due to the deep penetration as a result of procedural properties - one speaks of 2/3 (base material) and 1/3 (seam exaggeration) effect - a good economic use. This is superimposed by the possibility of using high energy densities, but also the possibility of high energy densities

Use of special welding powders for high welding speeds up to 2, 5 m / min.

One variant of submerged arc welding is sub-powder surfacing (U P-surfacing). Using this process, layers are welded onto a base material over a large area, for example to repair a roll. Although the process-related performance values, but not the high penetration rate, are particularly in demand for U P surfacing. The resulting burn-in profile leads to strong dendritic

Structure, which in turn has a tendency to crack formation in the present alloys and the associated hardnesses. Moreover, this means that, due to the high degree of mixing by the base material, the desired properties of the weld metal can only be expected from the third welding position. Also, as a result of the increased heat input with increasing residual stresses of the component and thus with Distortions can be expected. In summary, it remains to be said that the UP welding process for build-up welding is not necessarily given priority due to its very specific properties.

In order to make the penetration profile for the submerged arc welding more advantageous, strip electrodes are used as welding filler, after which the degree of mixing is reduced to about 25%. For this purpose, DE 22 38 321 and US 2,810,063, for example, proposes the use of a band electrode and the addition of metal powder in the weld pool. The band electrode tends to produce less burn-in. This property is based, among other things, in the oscillating arc or passing metal drops, which move back and forth at the strip edges. Furthermore, because of the tendency to have a larger cross section, the band electrode generates a lower current density and thus a lower penetration. The addition of metal powder has inter alia an energy-absorbing, that is cooling effect, so that the penetration can also be reduced in this way. However, here is the number of layers still with two or d rei

Execute weld beads on each other until a usable outer layer, that is, a wear layer is formed.

However, the use of a band electrode is limited to the extent that the availability of the respective band alloys is not given. This is compensated by an alloying welding powder, which, however, is generally only possible for total alloy contents of the weld metal up to about 15%. This disadvantage is eliminated by sintering belts, so that this alloy-neutral welding powder can be used.

However, sintered bands can not be produced in all alloys and are relatively expensive. In summary, it can be stated that the known UP surfacing methods, such as those used for processing rollers, rollers or similar elongate workpieces, are aimed at avoiding deep penetration

To minimize the mixing of the coating layer with the base material. Nevertheless, the alloy composition of a directly welded onto the base material layer through the molten base material is so adversely affected that multiple layers must be welded together to produce an outer wear layer that meets the requirements of alloy and hardness. For example, to create a wear layer of 2mm thickness at least two layers must be welded.

The disadvantage of known methods is therefore the number of layers to be welded on to produce a useful wear layer and the resulting material, energy and time expenditure.

The object of the present invention is now to propose a build-up welding method, which allows the welding of a wear layer in a single operation, without the need of welding several layers together. It is desirable that the only one produced according to the invention

Wear layer having the same or better properties, especially in terms of hardness, corrosion and / or wear as a conventionally produced outer wear layer in Mehrlagenauf welding technology.

According to the invention this object is achieved by a method having the characterizing features of claim 1. As a result of that the wire electrodes are filler electrodes having a core and a jacket electrode, the filler wire electrode having a higher alloy than the weld analysis of the wear layer to be welded, the jacket electrode of the filler electrode consisting of an alloy suitable for adhering the metal powder

Having magnetization properties, the following advantageous effect is achieved. Wire electrodes, in particular flux-cored electrodes, produce a deeper penetration compared to tape electrodes and a greater mixing with the base material, which is actually to be avoided according to the recommendations of the prior art. For example, blends of 40-50%, which are far beyond the recommendations of the prior art for U P build-up welding, are advantageous for the method proposed here. As a result of the deep penetration and the considerable supply of high-alloyed aggregates, the weld pool acts like a crucible and the melted base material is virtually converted into a single sufficiently alloyed useful layer. By suitable adjustment of the welding parameters, as well as amount and selection of the supplied metallic powder and / or the

Flux cored electrodes, the composition of a so welded in the deposition technique of the invention layer can be adjusted so that it corresponds to the composition of a third, by the conventional method with low mixing, welded layer. The use of flux-cored electrodes results in yet another possibility that is not given, for example, when using solid-state electrodes. If a high-alloyed solid wire is selected, this is usually not magnetizable. However, the high alloy content is needed for the preparation of the molten bath. The use of a

However, filler metal electrode makes it possible to use a readily magnetizable jacket electrode, on which the metal powder is good attach and accordingly a large amount of metal powder can be transported in the Schvveißbad. This could not be achieved with a solid earth electrode, since a solid wire electrode is either highly alloyed and consequently magnetically immutable, or low alloyed, and indeed magnetizable, but unsuitable because of the low content of alloying elements around the weld pool for the desired alloy content of the single aufzulegenden wear layer aufzulegenden. Also can be influenced in a comfortable manner on the thickness and diameter of the sheath electrode d the welding current density and thus the desired penetration, as well as the amount of adhering metal powder, for example, a thin-walled sheath electrode can be selected, resulting in a comparatively small cross-section and thus a comparatively high current density at g leichzeitig large

Mantle surface, ie adhesion surface for the metal powder results. The core transmits, except leakage currents, usually little welding current, so that the setting can preferably be done via the design of the sheath electrode. It is remarkable that such possibilities do not arise with a solid wire electrode, since the

Cross-sectional area and the lateral surface are in direct dependence on each other. It is further noteworthy that the method proposed here saves both material, energy and processing time since only a single layer has to be welded on. It was also found that the layer thickness and thus the order performance could be almost doubled using the method according to the invention.

In an advantageous embodiment of the proposed method has been found that can achieve particularly good results when the Fülld crystal electrode has about twice as high chromium content as the single wear layer to be produced. A For example, a typical wear layer that is welded to a continuous casting roll contains about 12-14% chromium, such that a proportion of about 24-28% chromium in the flux cored wire translates the molten base material and the supplied metal powder into a 12-14% wear layer % Chromium leads.

In an advantageous embodiment of the proposed method, it has been found that particularly good results can be achieved if the filler wire electrode has an approximately twice as high nickel content as the single wear layer to be produced. A typical wear layer, which is welded onto a continuous casting roll, contains for example about 3-4% nickel, so that a proportion of about 6-8% nickel in the flux-cored wire leads to a transformation of the melted base material and the supplied metal powder into a wear layer with 3-7% nickel. 4% nickel leads.

In an advantageous embodiment of the proposed method, it has been found that particularly good results can be achieved if the flux-cored wire electrode has an approximately twice as high molybdenum content as the single wear layer to be produced.

A typical wear layer, which is welded onto a continuous casting roll, contains for example about 0.5-1% molybdenum, so that a proportion of about 1-2% molybdenum in the flux-cored wire leads to a transformation of the melted base material and the supplied metal powder into a wear layer 0.5-1% molybdenum leads.

In an advantageous embodiment of the present invention can be provided that the Fülldrahtelektrode has a circular cross-sectional area, wherein the diameter of the

Cored wire electrode is about 2 to 3.2mm. This comparatively thin cored wire electrodes have proven to be particularly advantageous for producing a deep penetration.

It is further provided for generating a deep penetration, that each Fülldrahtelektrode is acted upon with about 300 to 475 A welding current.

It may also be advantageously provided that the volume of the sheath electrode makes up about 70% of the total volume of the filling electrode.

In order to ensure magnetization of the jacket electrode, it is advantageously provided that direct current is applied to the filler wire electrodes, the + pole being applied to the filler wire electrode.

In an advantageous embodiment of the proposed method, it can be provided that the cored wire electrodes are supplied substantially parallel, but at a selected distance from each other. By selecting an optimized distance of the

Cored wire electrodes create the prerequisite for magnetic influence. In contrast to a band electrode, the possibility is also created that metal powder can be transported through the intermediate space between the two filling band electrodes into the weld pool. Accordingly, the supplied amount of metal-containing powder can be increased over the use of a band electrode.

Advantageously, it may further be provided that the filling electrode electrodes oscillate transversely to the welding direction. Through this

Measure can in particular a dendritic seam formation, the so-called dendrite strain, avoided and the degree of mixing be set. Ultimately, the crack resistance of the welded layer is increased overall by this measure. The low seam exaggeration due to the pendulum means equally low costs.

In an advantageous embodiment of the proposed method can be provided that the filler wire electrode in sum of the sheath electrode and core about a proportion of <0.08% carbon; 0.2-0.3% silicon; 0.6-0.8% manganese; 24-28% chromium; 6-8% nickel and 1 -2% molybdenum and 0, 1 to 0.3% vanadium. Such

The advantage of the composition is that, due to the expected mixing with the base material, the usual material composition of the wear layer for continuous casting rolls is 12-14% chromium, 3-4% nickel and 0.5-1% molybdenum. This example shows a possible selection of the alloying elements of the cored wire electrode in FIG

Reference to the base material, wherein the alloy selection should meet the requirement that the cored wire electrode should have about twice as high alloy as the aufzuschweißende wear layer.

In a further advantageous embodiment of the present method can be provided that the sheath electrode of the Fülldrahtelektrode about a proportion of <0.05% C; <0, 10% Si; <0.40% Mn; <0.015% P; <0.01 5% S has. A cladding electrode with the aforementioned alloy composition has primarily good magnetizability. This property is particularly advantageous because sufficient metal powder can adhere to the Fülld rahtelektrode, which is to be transported into the weld pool.

In a further advantageous embodiment of the present method can be provided that the composition of the Metal powder corresponds to the weld analysis of the wear layer to be welded. By this measure, an extremely homogeneous wear layer can be produced with regard to the alloy composition. This effect is based, in particular, on the fact that, for example, deviations in the quantity of the metal powder supplied, for example due to a malfunction of the feed device, will in principle result in no deviation in the alloy composition of the wear layer to be produced. At most, the thickness of the wear layer will change as less metal powder has been supplied is.

Advantageously, it can be provided that the metal powder has ferritic components, so that the metal powder can be coupled in an advantageous manner in the magnetized jacket electrodes which are under current.

It is further advantageously provided that the metal powder is supplied de-energized, so that it is melted by the process heat of the weld pool and can extract excess heat from the weld pool. Accordingly, by metering the metal powder, the sweat bath temperature and thus the formation of the weld pool can be appropriately influenced.

In a further advantageous embodiment of the proposed

Method may be provided that a metal powder is used in gas or water-atomized form. This results inter alia in the advantage that gas atomized powders are easier to promote, since they are fine-grained and round. In contrast, metal powder in a water-dark form is more favorable. Alternatively, it can also be provided that a metal powder in agglomerated form is used. Agglomerated Metaiipuiver has the advantage that it can be produced in any alloy composition.

In an advantageous embodiment of the proposed method, it can be provided that the metal powder has a content of <0.08% carbon; 0, 1 5-0.3% silicon; 0.4-0.8% manganese; 12-14% chromium; 3-4% nickel; 0.5-1% molybdenum and 0, 1 to 0.3% vanadium. In accordance with the invention, this can then correspond to a composition of the wearing layer to be welded on. Also shows here the ratio between "higher" and "lower" alloy between the Fülld rare and the metal-containing powder. It can be seen that, in particular, an approximately twice as high proportion of chromium, nickel and molybdenum in the flux-cored wire electrode leads to the desired alloy composition of the wearing layer.

In a further advantageous embodiment of the present method can be provided that an alloy-neutral welding powder is used. An alloy neutral

Welding powder has no significant influence on the alloy composition of the wear layer to be welded. In principle, therefore, a possible interference factor is eliminated by an alloy-neutral welding powder.

It can also advantageously be provided that the welding powder is a mineral welding powder, so that the welding powder can advantageously support metallurgical tasks, such as, for example, the shaping of the weld seam. The Schweißpu lver prevents the drainage of the liquid welding pool. To further optimize the proposed method, it can be provided that a welding powder is used whose slag, taking into account the use of rotationally symmetrical components, has a high viscosity and good slag solubility at elevated working temperature. This measure further increases the process reliability of the proposed UP hardfacing method.

It can also be advantageously provided that the welding powder about a proportion of 10% SiO ₂ + TiO ₂ ; 35% Al ₂ O ₃ +

MnO; 50% CaF ₂ . The proposed welding powder allows a good slag removal even at a working temperature up to 350 ° C. Furthermore, the proposed welding powder supports the requirements of the viscosity of the slag, so that it forms the seam and does not run off, resulting in a heavy

Slag solubility would lead.

In a particularly advantageous manner, the proposed method for processing of symmetrical rotary bodies, such as rollers from cold rolling mills. In this connection, it can be advantageously provided that the base material is a roller, wherein the filler wire electrodes, the metal powder and the welding powder are fed through a welding head, wherein the roller is rotated below the welding head, wherein the welding head in the longitudinal direction of

Roll is advanced.

In a further advantageous embodiment of the present method it can be provided that the wear layer of about 25% welding wire, 25% metal powder and 50% of the melted

Surface of the workpiece exists. This extremely high melting of the workpiece surface is actually only due to the According to the invention proposed method achievable. However, it can therefore be advantageously utilized a considerable proportion of the material material for the production of the wear layer.

Further features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings. Show in it

1 shows a welding head for a method according to the invention for welding a wear layer onto a base material;

Fig. 2 is a schematic representation of a welding system with a welding head to the embodiment of the invention

process;

3 is a schematic representation of the layer thicknesses using the example of a roll;

4 shows a section through a trial roll (segment) produced by the method according to the invention;

5 shows a section through a trial roll (segment) produced by the method according to the invention;

Fig. FIG. 6 shows a section through a test roller (segment) produced by the method according to the invention with marked hardness measuring points; FIG.

7 shows a section through a test roller (segment) produced by the method according to the invention with marked hardness measuring points;

8 is an enlarged view of the sample according to FIG. 5 and 6 with marked material analysis measuring points; Fig. 9 is a schematic cross-sectional view of a

Füiid rahteiektrode for the inventive method.

First, FIG. 1, reference is made.

A welding head 1 for carrying out the method according to the invention essentially comprises a first feed device 2 for a first Fülld frame electrode 5 and a second Fülldrahtelektrode 5a, a second feeder 3 for welding powder 6 and a third feeder 4 for metal powder 7. In addition, the welding head has a power connection S for the required electric welding current. Both the first flux-cored electrode 5 and the second flux-cored electrode 5a are supplied with welding current. Also, the cored wire electrode 5 and 5a, metal powder 7 and

Welding powder 6 stored in suitable reservoirs and fed to the welding head 1 by suitable means.

The first feeder 2 for the filler wire electrodes 5 and 5a is preferably a multi-wire type suitable for supplying at least two flux-cored electrodes 5 and 5a substantially in parallel with the cored wire electrodes 5 and 5a being preferably oriented transversely to the welding direction. Also conceivable is the supply of further flux cored electrodes via the same or via one or more additional welding heads. It is also conceivable, of course, to supply the first filling electrode 5 via a first welding head and the second filling wire electrode 5a via another welding head.

The preferred embodiment of the welding head shown here

1 is further equipped with a shuttle, which the welding head 1 in a pendulum motion relative to the Base material can put. When pendulum comes, for example, in a base material in the form of a roller 8, a direction parallel to the longitudinal axis of the roller 8 in question. Welding is usually done with oscillating welding head up to a seam width of about 55 mm. By this measure, in particular a dendritic seam formation, the so-called dendrite strain, can be avoided. Finally, the crack resistance of the welded layer as a whole is increased by this measure. By the here proposed embodiment of the welding head 1, in particular by the above

Two-sided feed and the pendulum device, weld seams of about 50mm width and a thickness of about 5 to 6mm can be produced. The thickness refers here to the thickness above the original G round material surface.

In the preferred embodiment of the present invention proposed here, the cored wire electrode consists of a tubular sheath electrode 11 and a core 10 of mineral and / or metallic components. The cored wire electrodes 5, 5a are in seamless or form-closed

Execution purposefully alloyed. The Fülldrahtelektroden 5, 5a have a total diameter of 2.0 to 3.2 mm 0 on. The circular cross-sectional shape of the cored wire electrodes contributes to the desired deep penetration and high dilution.

The power connection S is supplied with a welding current of about 600 - 950 A, which allows ablation rates of 18 - 30 kg / h. The current range refers to both cored wire electrodes 5 and 5a in total, so that - assuming that each cored wire electrode is halfway with the supplied current is supplied - each Fülldrahtelektrode with about 300 to 475 A welding current is applied.

The use of flux-cored electrodes 5, 5 a instead of solid-wire electrodes is not only based on alloy technology

Aspects, but at the same time offers the advantage of

Performance increase, since this can reduce the current-carrying cross-section and increase the current density, whereby the Abschmelzleistung can be increased.

From the geometric conditions of the cored wire electrode 5, 5a, in particular from the cylindrical shape of the sheath electrode 1 1 and the selected welding current range results in a high average welding current density. The welding current density is substantially dependent on the cross-sectional area of the sheath electrode 1 1, since the core 10 transmits primarily leakage currents. The relatively high welding current density contributes to the inventively desired deep penetration and the large dilution.

In a comparison between a solid wire and one or two cored wires, assuming an approximately equal current density, another advantage of cored wires suitable for the comparatively larger circumference and the consequent greater suitability for adherence of metallic powder is shown

Jacket surface is due.

For example, two thinner flux-cored electrodes are used, which have a larger circumference compared to a thicker wire of the same surface area (see Table 1):

Table 1

A larger wire circumference leads to increased power at the same current density

Adherence of metal powder 7, assuming its magnetizability, at the same magnetic field strength for better and denser attachment. Practical preliminary tests have shown a powder-to-wire ratio of about 0.8-1.0: 1, which means that the deposition rate is at least as great as the amount supplied

Powder quantity could be increased.

A preferred composition of the flux-cored wire electrode 5 or 5a essentially contains the alloying elements [in%] listed below in tabular form (Table 2):

Table 2

The composition of the Fülld rahtelektrode 5, 5a is to be understood as the sum of the alloying elements, which is supplied from the molten core 10 and the molten shell electrode 1 1 to the weld pool. It is too Consider that the core 10 may well have different alloying shares than the sheath electrode 1 1.

For the tubular sheath electrode 1 1, a different from the core 10 alloy composition is selected, which has mainly a good magnetizability. This property is particularly important so that sufficient metal powder 7 can adhere to the Fülldrahtelektrode 5, 5a, which is to be transported into the weld pool. A preferred composition of the jacket electrode 1 1 of the filler electrode 5 or 5 a has at least the following tabular (Table 3) set up alloying elements [in%]:

Table 3

Due to the different composition, the filling electrode 5, 5a can be adapted to different requirements. Here are different alloys for different applications possible. Ultimately, the customer can determine the alloy, or the task of the workpiece largely dictates the alloy. Essentially, however, it is important that the cored wire electrode 5, 5a has a higher alloy than the wear layer 9 to be produced and, as a rule, also as the base material 8, so that the base material 8 in the oversized weld pool passes through the

Addition of higher alloy flux-cored electrodes 5, 5a is alloyed and forms after cooling a wear layer 9, the sum of the desired alloy composition, in particular a comparable or even better alloy composition Shen as a third layer after conventional U P-Auftragschwei Shen welded layer, comprising. The cored wire electrodes are compared to the Soiianaiyse überiegiert to compensate for the high penetration (mixing by the base material 40-50%) alloy technology, d. H. Already in the first situation, the desired weld analysis is realized.

The use of a cored wire electrode according to alloyed massive rahtes would be conceivable, but encounters the following problems:

1) Such an alloy is not available on the market and would cause immense costs as a special production

2.) The deformability is pulling or rolling technically possible only with suitable intermediate annealing.

3.) The chemical composition of such a wire limits the magnetizability, because its structure has an austenite content of about 30%, which is not known to be magnetizable.

The reverse way of doing the weld metal alloy exclusively via the metal powder also fails due to its limited magnetizability.

The electroless, magnetically supplied metal powder 7 should correspond to the wear layer 9 to be welded on from a qualitative point of view of the alloy. Conceivable, of course, are also predetermined, deviating from the weld analysis of the single-layer welded wear layer 9 compositions of the metal powder 7 for setting desired metallurgical

Parameter. For this purpose, it may be advantageously provided that the third feed device 4 for the metal powder 7 is provided with a metering device. and / or mixing device is equipped, so that it can be ensured that the supplied Metaiipulver 7 in a predeterminable composition, preferably exactly the Schweißgutanalyse a aufzuschweißenden wear layer 9 corresponds. An influence on the alloy composition by the welder is thereby prevented and the homogeneity of the welded layer is increased sustainably, which leads to a uniform expansion behavior over the entire layer thickness. The metal powder as Vorschmelzlegierung according to the weld metal is present in gas or water-evaporated form. It should have no spruce grain to be fed easily via a metering and / or mixing device can. Another possibility is to agglomerate the metal powder, which has the advantage of producing the alloy in any desired manner. Necessary for both water atomized and agglomerated metal powder suitable dosing equipment, which is explained by the grain shape and the relatively low bulk density. For coating, for example, continuous casting rolls, an alloy composition of the metal powder is proposed as follows [in%]:

C Si Mn Cr Ni Mo V

<0.08 0, 15 - 0, 4 - 0, 8 1 2-1 4 3 4 0,5-1 0, 10 0,30 0, 30

Table 4

Ultimately, this is a specific application of the proposed method according to the invention, d. H . for other applications, the alloy composition may of course differ depending on the wear layer to be welded on. At the welding powder are the requirements to raise that it is alloy neutral! is present. In addition, their schiacke, taking into account the use of rotationally symmetrical components have a high viscosity and good slag solubility even at elevated working temperature. In addition, will be a good one

Slag disposal even at a working temperature up to 350 ⁰ C required. Further, there is a requirement for the viscosity of the slag to form the seam and not drain, which would result in severe slag solubility.

The aforementioned requirement profile is fulfilled by a flouride-based powder of the following composition (Table 5).

Table 5

Basicity according to Boniszewski: ~ 1, 8

FIG. 2 shows a surfacing system for plating a roll 8. An inventive welding head 1 can be seen, which is arranged above the roller 8. Also, the corresponding components, such as control devices, reservoirs for Fülld frame electrode 5 and 5a, metal powder 7 and welding powder 6, and the feed device for the welding head 1 according to the invention can be seen.

The method for welding a wear layer 9 onto a base material is illustrated by the example of a roller 8 as a base material as follows. The results given in each case are from a first series of experiments. It should be noted that the results of the first series of experiments are still incomplete Expectations of aufzuschweißenden wear layer corresponded, in particular, the Chrorn-Anteii in the wear layer 9 was not high enough. Nonetheless, the results are to be cited and explained for illustrative purposes.

The roller 8 is set in rotation at a predetermined rotational speed. With simultaneous and well-dosed feeding the first Fülldrahtelektrode 5 and the second Fülldrahtelektrode 5 a, metal-containing powder 7 and welding powder 6 is an arc between the Fülldrahtelektroden 5, 5 a and

Role generated. A local weld pool forms on the base material surface, comprising essentially a mixing zone and a welding bead, in which both the filler electrodes 5 and 5a, metal powder 7 and a local area of the base material 8, ie the roll surface, are melted and after Cooling forming a wear layer 9 and a small amount of slag. The welding powder 6 contributes advantageously to the formation of the weld pool and to dissipate heat. According to the feed of the welding head 1, the roller is thread-shaped coated with the wear layer 9, which form a full-wearing layer due to the g leichzeitigen supply of two cored wires, ie a first Fülldrahtelektrode 5 and a second Fülldrahtelektrode 5 a, metal-containing powder 7 and welding powder 6 so that no further layer has to be welded on.

In particular, in the proposed method according to the invention, the otherwise rather disadvantageous cover profile of the UP-wire welding is advantageously exploited, such that a degree of mixing of about 40-50% results, so that in this method about 40-50% of the predominantly unalloyed Workpiece can be converted into high quality weld metal. Overall, a wear layer 9 may be formed, which consists of about 25% welding wire, 25% metaihaitigem powder and 50% of the molten surface of the workpiece. This welding technology achieves usable weld metal thicknesses of 6 to 12 mm by single-layer welding. The crystal orientation is almost perpendicular to the component surface, d. H. the critical training of the dendritic midrib does not occur. Such a design of the seam profile offers increased crack resistance, especially in the case of the complex stress of continuous casting rolls, ie essentially from operating temperature,

Thermal shock, corrosion wear and dynamic load exists.

Overall, a method is proposed, which allows individual weld metal alloys for different applications, in particular for the hard coating. In particular, a wear-resistant wear layer 9 can be produced in only one welding pass. There are no further layers, as provided in the prior art, to be welded. Nevertheless, a homogeneous structure results in the one wear layer

9 with a uniform analysis over the entire layer area.

In the embodiment proposed here, using the example of build-up welding on a cold-rolling roller (cf., in particular, FIG. 3), a total remelted area 20 of approximately 10 mm results. The remelted area is composed of a transition region 21 between the base material 8 and the use layer 9 and the wear layer 9 as such. The wear layer 9 with a thickness of about 5 mm is shown here already minus a machining allowance 22 of about 2-3 mm. The machining allowance 22 is removed in a machining process, so that a effective wear layer 9 in the example chosen here is about 5mm thick.

It can also be seen the Aufschweißungseffekt, provided that the thicknesses of the individual layers of the surface 23 of the

Base material 8 are considered. Overall, about 3 mm of the wear layer 9 are arranged below the surface 23 of the base material. Above the surface 23 of the base material, a coated layer 24 of about 5mm is indicated, wherein the applied layer 24 of a portion of the wear layer 9 and a

Machining allowance 22 of about 2-3mm.

The Fig. Figures 4 and 5 illustrate a segment of a roll processed in accordance with the method proposed by the invention, the roll segment being suitably cut out of the roll.

Also shown in Figs. 6 and 7 is a segment of a trial roll which has been sawn and ground. To make the hardness profile visible, hardness tests were carried out at those locations marked with numbers, the results of which are shown in Table 6 below. It can be seen that over the entire cross section of the wear layer there is a desired even hardness distribution.

Table 6

Also results in a very homogeneous composition with respect to other metallurgical parameters, which were determined according to the Fig. 8 at a abgefräßten specimen. Taking into account the resulting measured values in accordance with Table 7 below, a very homogeneous distribution of the alloying elements listed can be taken, so that the single wear layer produced according to the invention can ensure usability, in particular for downstream machining processes over the entire cross section. The analysis was carried out with a mobile spectrometer at seven measuring points, at different positions of the test piece.

Table 7

In a further series of experiments the following results could be achieved. It should be noted that the experience of the first series of experiments could be used to optimize the process parameters of the second series of experiments. In particular, by increasing the chromium content in the core of the filler wire electrodes 5, 5 a, a preferred chromium content in the wear layer 9 could be adjusted.

The analytical finding of a wear layer welded on according to the method of the invention onto a continuous casting roll is as follows [in%] (Table 8). The measuring points have been set analogously to the test piece according to FIG. 8.

Table 8

The result is a very even distribution of elements.

Hardness measurements were also carried out in the second series of tests. The respective measured values have been taken at comparable measuring points according to FIGS. 6 and 7. This results in the following hardnesses according to Table 9:

Table 9 SG = weld metal (wear layer)

Ü = transition

GW = base material

The result of this study is a very homogeneous one

Hardness distribution that meets the requirements. Only measuring point 16 is below the hardness level, because this measuring point was taken from the base material. The downstream cutting machining process is thus ensured over the entire cross section.

The advantageous economy of the proposed method according to the invention can be illustrated by the following exemplary comparison with a conventional UP-surfacing. A roll with a diameter of 300mm, one

Length of 1000mm and a wear layer is pre-twisted in the conventional U P-band welding process to about 290mm diameter and then welded three layers. The roll diameter after welding is 306mm, which corresponds to an applied amount of 58.8kg weld metal.

In a method proposed according to the invention, the same roll is pre-stretched to 296 mm. After welding one wear layer, the roll diameter is 306mm. However, this corresponds to an applied amount of 37, 12kg

Weld metal. The result is a saving of 21, 7kg of weld metal compared to the method according to the prior art, which corresponds to a percentage saving of 36.9%.

Even considering the so-called Abschmelzleistung a conventional UP-band welding with about 1 3kg / h (U P- wire welding about 8kg / h) is proposed by the here inventive method to achieve a Abschmelzleistung of about 20kg / h, which means a power increase of 54% over the conventional method.

Also results from the proposed inventive

Method a favorable shortening of the welding time, which is based in particular on the fact that only one layer, instead of three layers must be welded. For a role exemplified here, the welding time in the conventional UP-band welding process is about 271 minutes. In contrast, the

Welding time with the help of the proposed method according to the invention about 1 1 1 minutes. The time saved is about 160 minutes, which corresponds to a percentage increase in performance of about 59%.

Claims

claims: 1 . Method for welding a wear layer (9) to a base material, wherein - A first wire electrode (5) and at least one second wire electrode (5a) each acted upon by a welding current and the base material to produce a common welding pool is continuously supplied, wherein - Metal powder (7) is supplied to the weld pool, wherein - the weld pool is supplied with welding powder (6), characterized in that - It is in the wire electrodes to Fülldrahtelektroden (5, 5a), comprising a core (10) and a jacket electrode (1 1), wherein the flux-cored electrode (5, 5a) has a higher alloy than the weld analysis of the wear layer (9) to be welded on, wherein - The sheath electrode (1 1) of the Fülldrahtelektrode (5, 5 a) consists of an alloy which has suitable for the adhesion of the metal powder (7) magnetization properties. 2. The method according to claim 1, characterized in that the Fülldrahtelektrode (5, 5a) has an approximately twice as high chromium content as the aufzuschweißende wear layer (9). 3. The method according to any one of the preceding claims, dad urch in that the filler wire electrode (5, 5 a) approximately having twice as high nickel content as the wear layer to be welded (9). 4. The method according to any one of the preceding claims, characterized in that the Fülldrahtelektrode an approximately twice as high molybdenum content as the aufzuschweißende wear layer (9). 5. The method according to any one of the preceding claims, characterized in that the Fülldrahtelektrode (5, 5a) has a circular cross-sectional area, wherein the diameter of the Fülldrahtelektrode (5, 5a) is about 2 to 3.2 mm. 6. The method according to any one of the preceding claims, characterized in that each Fülldrahtelektrode (5, 5a) is acted upon by about 300 to 475 A welding current. 7. The method according to any one of the preceding claims, characterized in that the volume of the jacket electrode (1 1) constitutes about 70% of the total volume of the Fülld frame electrode (5, 5a). 8. The method according to any one of the preceding claims, characterized in that the Fülldrahtelektroden (5, 5a) with DC are applied, wherein the + pole on the Fülld rare electrode (5, 5 a) rests. 9. The method according to any one of the preceding claims, characterized in that the Fülldrahtelektroden (5, 5a) are supplied substantially parallel, but at a selected distance from each other. 10. The method according to any one of the preceding claims, characterized in that the Fülldrahtelektroden (5, 5a) oscillate transversely to the welding direction. 1 1. Method according to one of the preceding claims, characterized in that the Fülldrahtelektrode (5, 5a) approximately one Proportion of <0.08% carbon; 0.2 to 0.3% silicon; 0.6 to 0.8% manganese; 24 to 28.0% chromium; 6 to 8% nickel, 1 to 2% molybdenum and 0, 1 to 0, 3% Vanad ium. 12. The method according to any one of the preceding claims, characterized in that the jacket electrode (1 1) of the Flux cored electrode (5, 5a) about a proportion of <0.05% C; <0, 10% Si; <0.40% Mn; <0.015% P; <0.01 5% S has. 13. The method according to any one of the preceding claims, characterized in that the composition of the metal powder (7) of the weld analysis of aufzuschwei sequent wear layer (9). 14. The method according to any one of the preceding claims, characterized in that the metal powder (7) has ferritic components. 15. The method according to any one of the preceding claims, characterized in that the metal powder (7) is supplied de-energized. 16. The method according to any one of the preceding claims, characterized in that a Metallpu lver (7) is used in gas or water-atomized form. 17. The method according to any one of the preceding claims, characterized in that a metal powder (7) is used in agglomerated form. 18. The method according to any one of the preceding claims, characterized in that the metal powder (7) about a proportion of <0.08% carbon; 0.15 to 0.3% silicon; 0.4 to 0.8% manganese; 12 to 14% chromium; 3 to 4% nickel; 0, 5 to 1% molybdenum and 0, 1 to 0.3% vanadium. 19. The method according to any one of the preceding claims, characterized in that an alloy-neutral welding powder (6) is used. 20. The method according to any one of the preceding claims, characterized in that a mineral welding is used ßpulver (6). 21. Method according to one of the preceding claims, characterized in that a welding powder (6) is used, the slag of which, taking into account the use of rotationally symmetrical components has a high viscosity and good slag solubility at elevated working temperature. 22. The method according to any one of the preceding claims, characterized in that the welding powder (6) about a proportion of about 10% SiO ₂ + TiO ₂ ; 35% Al ₂ O ₃ + MnO; 50% CaF ₂ . 23. The method according to any one of the preceding claims, characterized in that it is the base material is a roller (8), wherein the Fülld rahtelektroden (5, 5a), the Metal powder and the welding powder are fed through a welding head (1), wherein the roller (8) below the welding head (1) is rotated, wherein the welding head (1) in the longitudinal direction of the roller (8) is advanced. 24. The method according to any one of the preceding claims, characterized in that the welded-on wear layer consists of about 25% flux-cored wire (5, 5a), 25% metal-containing powder (7) and 50% of the molten surface of the material.